The invention relates to a wheel hub unit having a wheel hub, a wheel bearing and an outer joint part of a constant velocity universal joint which, at the hub end, comprises a shaft journal with shaft splines. The shaft journal is inserted into a through-aperture of the wheel hub. The through-aperture is provided with internal splines.
A wheel hub unit with the above-mentioned characteristics is known from EP 936 086 A2, for example, wherein the axial securing means between the wheel hub and outer joint part are provided in the form of a securing ring with a round cross-section. The securing ring is inserted into corresponding grooves in the internal splines, and in the shaft splines near the free end of the shaft journal at the outer joint part. In addition, there is provided a sealing ring which is slipped on to the shaft journal near the base of same and which sealingly engages a recess in the through-aperture of the wheel hub. For dismantling purposes, this type of axial securing means requires the outer joint part and, respectively, the journal to be pressed out of the wheel hub. In the course of this operation it is possible to damage the securing ring and also the grooves. Because the holding forces of such axial securing means are somewhat inadequate, axial security to prevent automatic axial unfastening of the connection in case of an axial impulse load no longer exists after re-assembly.
The present invention provides a wheel hub unit of the above-mentioned type with an improved axial securing mechanism. The axial securing mechanism is a securing ring which comprises a rectangular cross-section and which engages corresponding rectangular circumferential grooves at the shaft splines and in the internal splines. Also, at the shaft journal, near its base, there is provided a centering collar which, in a radially play-free way, engages the through-aperture of the wheel hub. The axial securing mechanism provides the necessary security against unintentional axial dismantling because neither the securing ring nor the grooves comprise radii or chamfers which allow automatic disconnection through axially pressing out of the outer joint part and journal. The axial securing mechanism allows the securing ring to be acted upon without causing damage in such a way that it can leave one of the grooves and enter the other groove completely, so that the parts, i.e. the hub and shaft journal, can be displaced relative to one another and assembled without being obstructed. As a result of the rectangular securing ring which engages rectangular circumferential grooves, axial displacements are avoided. This is assisted by the centering collar which is attached at a relatively great axial distance therefrom and which accommodates radial forces of bending moments (secondary moments) occurring under torque. The connection is also noise-free.
According to a further embodiment, at the shaft journal, close to its base, there is slipped on a sealing ring which is sealingly positioned between the through-aperture of the wheel hub and the shaft journal. In this way it is possible to avoid fretting corrosion in the inter-engaging toothings. In this context, it is proposed according to an advantageous embodiment, at its end face, the shaft journal comprises a countersunk region which extends axially from its free end and projects beyond the circumferential groove. The shaft journal also comprises a radial notch which extends axially from its free end as far as the circumferential groove and into the countersunk region. Inwardly bent free ends of the securing ring extend through the notch into the countersunk region. In this way, the securing ring can be radially pulled together from the outer end of the wheel hub in such a way that it is able to enter fully the deep circumferential groove on the shaft journal, so that it simultaneously leaves the inner groove in the wheel hub, thus permitting both parts to be displaced relative to one another for dismantling purposes.
The inventive axial securing mechanism allows a defined annular gap to be determined between the bearing and the outer joint part. In this way, it is possible to avoid the formation of noise. The annular gap should be axially wider than the entire axial play of the securing ring in its circumferential grooves.
According to a first advantageous design, the wheel bearing comprises a double-row rolling contact bearing which comprises an inner bearing race which is slipped on to the wheel hub from the joint end, and which is axially held on the wheel hub by a radially outwardly pointing wheel hub beading at the joint end. In this embodiment, the wheel hub carries an integrally formed-on wheel flange.
According to a further design, the wheel bearing comprises a double-row rolling contact bearing which comprises an inner bearing race which is slipped on to the wheel hub from the wheel end, and which is axially held on the wheel hub by a radially outwardly pointing wheel hub beading at the wheel end.
Wheel bearings of this type can be produced with a large number of balls/rollers and with a permanent bearing pre-tension. The bearings can be ball bearing or tapered roller bearings.
Other advantages and features of the invention will also become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.